Engineering: Add language checks to build or CI

Ensure language used in code, telemetry, logs, or comments is en-US.

- This can either be a check as part of running dotnet build, or as part of the CI pipeline.
- This change needs to apply to all of the repos we maintain.

Start by reviewing this repository's existing dotnet build and CI configuration; the issue names no files or checks. Determine how language in code, telemetry, logs, and comments would be detected across all maintained repositories, with consistent en-US enforcement in build or CI defining completion.

Written by the indexing model from the issue text.